1. Field of the Invention
The present invention relates to chain conveyor assemblies of the type wherein a conveyor chain is driven so as to directly convey objects along a path determined by a supporting guide track for the conveyor chain. In particular, the present invention is directed to such chain conveyor assemblies wherein the conveyor chain is constructed to enable the chain to be flexed in two dimensions, e.g., about horizontal and vertical axes.
2. Description of Related Art
Chain conveyor assemblies of the aforementioned type have been in use for numerous purposes for a very long time and the construction of the conveyor chain of such assemblies is of key importance from several standpoints which involve competing factors. For example, as a major contributor to the cost of the chain conveyor assembly, the conveyor chain should be of as simple a construction as possible with a minimum number of wheels and pivot point connections. On the other hand, the great loads to which the chain will be subjected as the drive causes the chain to pull a load being transported by the chain conveyor assembly, as well as the need for stable guidance of the chain and load, has led to the development of conveyor chains and assemblies that are very costly to produce.
One simple chain design is disclosed in the chain carrier of Merz U.S. Pat. No. 993,313, wherein links consisting of an oval loop of rigid material is provided with an axle upon which is journaled a single bearing wheel. Alternate similar links are oriented at 90.degree. with respect to each other so that the bearing wheels form an alternating series of vertical and horizontal axis wheels. The chain is driven directly by sprocket wheels and the articles to be transported are carried directly on the chain between standards rising at each side of each link. Another chain having an alternating series of horizontal and vertical axis bearing wheels, to which attachments such as rods, flights, and chains may be attached for conveying of products, is one produced by the Atlas Chain Company. The chain links of the Atlas chain are formed by pairs of identical link elements, each of which is provided with a right angle bend so as to enable each link element of a pair of link elements to support a respective end of a journal shaft of both a horizontal axis and a vertical axis bearing wheel. However, such constructions are suitable only for conveyance of light weight products as the designs are neither stable nor strong enough to withstand heavy loading conditions without breakage.
Typically, when an application requires a capacity to operate under heavy loading conditions, an approach has been taken to increase the strength of the link elements and to use pairs of wheels instead of a single bearing wheel. Examples of such conveyor chain arrangements can be found in Michna U.S. Pat. No. 2,646,160, Freeman U.S. Pat. No. 3,496,784, and Willett U.S. Pat. No. 3,880,276. However, assemblies using such conveyor chains are more expensive due to the increased cost associated with producing such conveyor chains, and assemblies utilizing such chains are normally used where the load is either supported, centered directly above or suspended, centered, directly below the conveyor chain due to the stresses which would be applied if the chain were to pull a load connected laterally of the chain's path of movement.
A conveyor system wherein a plurality of pallets, trays, or other load carriers are conveyed along a path by means of a single drive chain in an arrangement wherein the pallets, trays, or the like are supported at one side by a chain and at the other side on a fixed track or runway extending parallel to the chain is disclosed in Burrows U.S. Pat. No. 3,343,499. The conveyor chain of this conveyor system also uses pairs of rollers, a horizontal axis pair of rollers being arranged in a cruciform arrangement in relationship to a pair of vertical axis rollers, and each cruciform arrangement of rollers is interconnected by a pair of link elements to which a traction drive coupling, consisting of a bracket and a pair of small horizontal axis rollers, is mounted. However, the conveyor chain of this patent, like those of the Michna, Freeman and Willett patents imposes a signficantly increased cost factor with respect to production of the overall conveyor system. It is also noted that the conveyor system of the Burrows patent is designed to appropriately orient articles being conveyed by pivoting of the pallet and not by two dimensional flexing of the drive chain.
Accordingly, it can be seen that there is a need for a chain conveyor assembly which can be produced relatively inexpensively as well as provide stable guidance of heavy loads while being able to flex in two dimensions. In particular, it is desirable to be able to use a chain conveyor assembly which does not require the use of pairs of wheels instead of a single bearing wheel.